Void Filling Joint Prosthesis And Associated Instruments

ABSTRACT

A method of forming a bone void for receipt of a prosthesis, comprising the steps of: inserting a stem of a reaming guide assembly into an intramedullary canal of a bone, the reaming guide assembly having first and second reamer guides disposed adjacent to each other, the first and second reamer guides being connected to an end of the stem; reaming the bone through the aperture of the first reamer guide to form a first bone void; inserting the lobe trial into the first bone void; and reaming the bone through the aperture of the second reamer guide to form a second bone void.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/412,536, filed May 15, 2019, which is a continuation of U.S.application Ser. No. 15/354,469, filed Nov. 17, 2016, now U.S. Pat. No.10,335,171, which is a continuation of U.S. application Ser. No.14/206,630, filed on Mar. 12, 2014, now U.S. Pat. No. 9,526,513, whichclaims the benefit of the filing date of U.S. Provisional PatentApplication No. 61/779,302 filed Mar. 13, 2013, all of which are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION

Joint replacement surgery is a common orthopedic procedure for jointssuch as the shoulder, hip, knee, ankle and wrist. Prior to implantingprosthetic components in a joint of a patient, a surgeon generally hasto resect at least a portion of the patient's native bone in order tocreate a recess or void for receiving at least a portion of theprosthetic components being implanted. During the process of resectingbone, a surgeon generally only resects the amount of bone that is neededin order to properly implant the prosthetic components in the joint.Once native bone is resected from a joint, it is gone forever. Thus, thesurgeon typically attempts to maintain as much native structuralintegrity of the joint as he or she can during the resection process.

When previously implanted prosthetic components fail for any one of avariety of reasons, a revision procedure is often necessary. An issuegenerally encountered by surgeons replacing joints during a revisionprocedure is the additional loss of native bone near the joint beingreplaced. This bone loss is typically due to movement of the componentor components after implantation or even degeneration or furtherdegeneration of the bone, which can form bone voids that haveunpredictable and non-uniform shapes.

When bone voids are observed in either the proximal tibia or distalfemur, or both, it is standard surgical practice to fill those voids aspart of the revision surgical procedure. The preferred practice is tofill those voids with weight bearing void fillers, typically made of animplant-grade metal such as titanium. However, because the bone voidsare typically irregular in shape, some preparation of the bone void areais typically required prior to implantation of the void filler. Thispreparation (typically by reaming, broaching or milling) ensures thereis sufficient room in the bone void for the void filler. An accurate fitbetween the shaped bone void and the void filler is also important forestablishing joint line, and allowing for weight bearing and boneremodeling during the recovery process.

Different methods are commonly used to attempt to prepare the bone voidarea to create an accurate fit between the shaped bone void and voidfiller. One method is to ream along the intramedullary (“IM”) axis,followed by broaching. Another method is to ream along the IM axis,followed by freehand burring or rongeur bone removal, which may also befollowed by broaching. Problems with these methods include that reamingis performed on the IM axis only, so that void areas at a distance fromthe IM axis, which commonly occur, can only be resected using manualmethods. Moreover, broaching generally has at least two problems. First,a manual operation can be time consuming, particularly in cases ofsclerotic bone, which exposes the patient to an increased risk ofinfection and longer recovery. Second, in the case of large bone voids,broaching generally needs to be performed in a multi-step processbecause attempting to remove high volumes of bone in a single broachingstep generally requires high impact forces to the bone. Also, freehandbone removal, either powered or unpowered, such as with a burr orrongeur, often does not produce accurate void shapes to receivepredefined prosthetic components. A typical result is that areas remainwhere the outer walls of the void filler do not contact the void, whichmay lead to undesirable stress distribution and possible loss of boneregrowth. Also typical is the time consuming requirement of iterativebone removal, with multiple checks against the void fillers, to obtain acorrect fit.

Occasionally the bone loss or bone deformity is so significant that thesurgeon must resect a portion of bone along its length and supplementthe bone loss with a bone augment. Since the surgeon typically attemptsto preserve as much native bone as possible, the result of the resectionis typically a bone that has multilevel plateaus, where the bone augmentis commonly placed between the joint prosthesis and one plateau in orderto augment the missing bone, and the prosthesis itself is placed againstthe other plateau. However, this resection generally does not eliminatethe need for a void filler. Generally, the bone void extends through themultilevel plateaus, which creates an area where the void filler wouldbe exposed and would interfere with the placement of the bone augmentwhen implanted. Unfortunately, this situation is often unpredictable asthe surgeon is often unaware of the need to augment until the previousprosthesis has been removed.

Thus, there is a need for a bone void filler that is adaptable to beused in both a joint revision procedure requiring a bone augment so asto not interfere with the placement of the augment and a joint revisionprocedure where a bone augment is not needed.

BRIEF SUMMARY OF THE INVENTION

According to a first embodiment of the present invention, a bone voidfilling prosthesis is disclosed herein. The bone void filling prosthesisincludes a body that includes an aperture extending therethrough, aplurality of legs each connected to the body. Each of the legs includingat least one selectively removable portion for adjusting a length ofeach of the plurality of legs.

Further, the at least one selectively removable portion may include afirst portion and a second portion. The first portion may be constructedfrom weaker material, while the second portion maybe constructed fromstronger material. The first portion and second portion may be layeredalong the length of the at least one of the plurality of legs.Additionally the weaker material may be porous titanium including afirst porosity. Further, the stronger material may be porous titaniumincluding a second porosity. The first porosity may be greater than thesecond porosity. Additionally, the weaker material is visually distinctfrom the stronger material.

Continuing with the first embodiment, each leg may include a pluralityof selectively removable portions layered along the length of each leg.Further, the body may be cylindrically shaped and the prosthesis mayinclude two legs, and each of the two legs may include a plurality ofselectively removable portions. Further, each of the two legs may besubstantially frustoconically shaped and one end of each of the two legsmay be partially integrated with the central body. Additionally, the twolegs may be separated by a space forming a saddle for receipt of afemoral cam box of a femoral implant. The space may be in communicationwith the aperture of the central body. Also, one end of each of the twolegs may further include a conical portion extending from the first end.The conical portion maybe partially integrated with the central body.

According to another embodiment of the present invention, a bone voidfilling prosthesis that includes a substantially cylindrical body havingan aperture extending therethrough and an exterior surface disposedopposite the aperture. Also, included is a first substantiallyfrustoconical leg having a first end and a second end. The first endbeing integrated with the exterior surface such that the first legextends away from the central body. The second end having at least onefirst selectively removable portion for adjusting a length of the firstleg. Further included in the bone filling prosthesis is a secondsubstantially frustoconical leg. The second substantially frustoconicalleg includes a first end and a second end. The first end of the secondleg may be integrated with the exterior surface such that the second legextends away from the central body. The second end of the first leg mayinclude at least one second selectively removable portion for adjustinga length of the second leg.

Further, the first leg may include a plurality of first selectivelyremovable portions layered along the length of the first leg, and thesecond leg may include a plurality of second selectively removableportions layered along the length of the second leg. Additionally, eachof the plurality of first selectively removable portions may include afirst portion and a second portion. The first portion may be constructedfrom weaker material, and the second portion may be constructed fromstronger material. The first portion and second portion may be layeredalong the length of the first leg. Each of the plurality of secondselectively removable portions may include a first segment and a secondsegment. The first segment may be constructed from weaker material, andthe second segment may be constructed from stronger material. Also, thefirst segment and second segment may be layered along the length of thesecond leg.

Continuing with this embodiment, the weaker material may include poroustitanium that may include a first porosity. Further, the strongermaterial may be porous titanium that may include a second porosity. Thefirst porosity may be greater than the second porosity. Additionally,the weaker material may be visually distinct from the stronger material.

The two legs may be separated by a space forming a saddle for receipt ofa femoral cam box of a femoral implant. The space may be incommunication with the aperture of the body. Additionally, the firstends of each of the first leg and second leg may further include conicalportions integrated with the body.

According to one embodiment of the present invention, a method offorming a bone void for receipt of a prosthesis. The method may includeinserting a stem of a reaming guide assembly into an intramedullarycanal of a bone. The reaming guide assembly may include first and secondreamer guides disposed adjacent to each other. The first and secondreamer guides may be connected to an end of the stem. Further includedin the method is reaming the bone through the aperture of the firstreamer guide to form a first bone void. The method also includesinserting the lobe trial into the first bone void. Additionally includedin the method is reaming the bone through the aperture of the secondreamer guide to form a second bone void.

Further, the first and second reamer guide may each include an aperturedefining a sidewall and a slot extending along the length of thesidewall. The slot may be in communication with the aperture.Additionally, the method may include the step of loading a reamerthrough the slot of the first reamer guide into the aperture of thefirst reamer guide. Further, the method may include the step of loadinga lobe trial through the slot of the first reamer guide into theaperture of the first reamer guide. Another step that may be included isthe step of loading the reamer through the slot of the second reamerguide into the aperture of the second reamer guide

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 shows a perspective view of one embodiment of a void fillingprosthesis.

FIG. 2 shows a front view of the void filling prosthesis of FIG. 1.

FIG. 3 shows another perspective view of the void filling prosthesis ofFIG. 1.

FIG. 4 shows a side perspective view of the void filling prosthesis ofFIG. 1.

FIG. 5 shows a top perspective view of another embodiment of a voidfilling prosthesis of FIG. 1.

FIG. 6 shows a bottom perspective view of the void filling prosthesis ofFIG. 5.

FIG. 7 shows a side view of the void filling prosthesis of FIG. 1interfacing with a femoral component.

FIG. 8 shows a rear view of the void filling prosthesis of FIG. 1interfacing with a femoral component.

FIG. 9 shows a side view of the void filling prosthesis of FIG. 5interfacing with a femoral component.

FIG. 10 shows a top perspective view of the void filling prosthesis ofFIG. 5 interfacing with a femoral component.

FIGS. 11-19 show a method and instrumentation for forming a bone void toreceive the prostheses of FIG. 1 and FIG. 5.

DETAILED DESCRIPTION

FIGS. 1-4 depict a first embodiment of a void filling prosthesis 10. Thevoid filling prosthesis 10 includes a central body 11, a medial leg 13,and a lateral leg 12. In another embodiment, the void filling prosthesis10 may include a central body and only a medial leg 13 or lateral leg12. The central body 11 is generally cylindrical. However, thiscylindrical shape may take the form of a portion that has a constantdiameter and a portion that is slightly tapered such that it isgenerally frustoconical. The central body 11 includes an aperture 18that extends through the central body 11 in order to allow the passageof an IM stem of a femoral component 30. This aperture 18 forms a wall19, which is integrated with the lateral and medial legs 12, 13 forminga monolithic structure.

The lateral and medial legs 12, 13 may be offset posteriorly from amedian transverse axis of the central body 11. Further, the lateral andmedial legs 12, 13 may be located in close proximity, but may beseparated generally by a space 17 that penetrates through both legs andforms a saddle-like structure in order to provide clearance for afemoral cam box 33 of a femoral component 30. This space 17 forms innersurfaces 15 a-d that abut the femoral cam box 33 when implanted. Theseinner surfaces 15 a-d may be flat, planar walls, or they may be terracedto provide surfaces conducive for bonding with bone cement. Further,inner surface 15 d may be obliquely angled with respect to thelongitudinal axis of the central body 11 in order to account for theangle of the IM stem (not shown) with respect to the cam box.

Further geometric features may be incorporated into the medial andlateral legs 12, 13 in order to provide clearance for the structure ofthe femoral component 30. For instance, inclined surfaces 14 a-d may befashioned into each leg in order to provide clearance for a boneinterface surface 35 of the femoral component 30.

The remainder of the lateral and medial legs 12, 13 that has not beenshaped to form clearance space is depicted as having a generallyfrustoconical profile. This geometric profile is preferred in order toconform more closely to bone voids created by the reaminginstrumentation. However, this is merely an example of a geometry thatthe medial and lateral legs 12, 13 may form. The legs 12, 13 may haveother geometries, such as box-like geometries. Further, the medial andlateral legs 12, 13 may be symmetric with respect to one another, orthey may be asymmetric where one leg 12, 13 may be larger than the other12, 13 and/or one leg 12, 13 may have a different geometry. A conicalstructure 16 a-b may be disposed at one end of each of the lateral andmedial legs 12, 13. This conical structure 16 a-b may help preventrotation of the prosthesis 10 when implanted in the bone and help theprosthesis 10 settle into the proper orientation and more closelyconform to the void formed by the reaming instruments.

Referring to FIGS. 1-4 and 7-8, each leg 12, 13 is shown to include tworemovable portions 20 a-d at an end of each leg 12, 13. While tworemovable portions 20 a-d are shown, this is merely an example. Each leg12, 13 may include any number of selectively removable portions 20 a-d,including just one. Alternatively, one leg 12, 13 may include at leastone selectively removable portion 20 a-d while the other leg 12, 13 mayhave no selectively removable portions 20 a-d. Where one or moreselectively removable portions 20 a-d is removed from a leg 12, 13, thelength of the leg 12, 13 is decreased in order to make room in the jointcavity for a bone augment, for example. This removability provides theoperator the operating room capability and flexibility to configure thevoid filling device 10 to work in conjunction with a bone augment, oralternatively work where no augment is needed. Thus, each selectivelyremovable portion 20 a-d is shaped to conform to the geometries of thevoid filling prosthesis 10 as though they will never be removed.Further, where these portions 20 a-d are not removed, they providestructural support to the prosthesis 10.

Where there are multiple selectively removable portions 20 a-d, they arelayered along the length of each leg 12, 13 as far as needed toaccommodate a bone augment. Each selectively removable portion 20 a-dmay have a first section 22 a-d made from a weaker material and a secondsection 21 a-f made from a stronger material, where the two sections 21a-f, 22 a-d are layered along the length of each leg 12, 13. In apreferred embodiment, the weaker and stronger material may be made fromthe same metallic material, but the weaker material may have a higherporosity than that of the stronger material allowing for a seamlesstransition between these two sections 21 a-f, 22 a-d, but providing aregion for easy separation. Separation is made easier by the fact thatthe more porous material is easier to separate and that the two sections21 a-f, 22 a-d are visually recognizable indicating the separationlocation. In one embodiment, the separation location may be designatedby a small chamfer to receive a cutting blade between the first section22 a-d of one selectively removable portion 20 a-d and the secondsection 21 a-f of another selectively removable portion 20 a-d. Anexample of the porous metallic material may be titanium, titanium alloy,stainless steel, cobalt chrome alloys, tantalum or niobium formed bydirect laser remelting as described in U.S. Pat. No. 7,537,664 titled“Laser-Produced Porous Surface,” the entirety of which isincorporated-by-reference herein fully set forth herein and which isassigned to the same entity as the present invention. Additionalexamples are disclosed in U.S. application Ser. Nos. 11/027,421, filedDec. 30, 2004, 11/295,008, filed Dec. 6, 2005, and 13/441,154, filedApr. 6, 2012, and U.S. Pat. Nos. 8,350,186 and 8,147,861, the entiretiesof which are incorporated-by-reference herein as if fully set forthherein.

In an alternative embodiment, the weaker material may have the sameporosity as the stronger material, but may be constructed from amaterial that has a lower modulus than the stronger material. In anotherembodiment, the entire void filling prosthesis 10 may be constructedfrom a porous metallic material including the selectively removableportions 20 a-d with little or no variations in the porosity, but thatthe selectively removable portions 20 a-d have score marks to designatethe cutting points. In a further embodiment, the first section 22 a-dmay have an outer shell that is the same porosity as the remainder ofthe void filling prosthesis 10, and an interior portion constructed fromthe weaker material.

These selectively removable portions 20 a-d may be removed by cuttingalong the weaker section 22 a-d generally parallel and adjacent thestronger section 21 a-f of another selectively removable portion 20 b,20 d that is more proximate the central body using a cutting device. Forinstance a cutting device may be a guillotine-like device, an example ofwhich is disclosed in U.S. application Ser. No. 12/002,002, filed Dec.13, 2007, the entirety of which is incorporate-by-reference herein as iffully set forth herein. Where the selectively removable portion 20 b, 20d is the last selectively removable portion along the length of thatparticular leg 12, 13, the leg 12, 13 may have a layer of strongermaterial 21 c, 21 f just adjacent to the weaker section 22 b, 22 d ofthat selectively removable portion 20 b, 20 d to facilitate removal.

The remainder of the void filling prosthesis 10 may also be partiallyconstructed from porous metallic material as described above. In oneembodiment, the surfaces in contact with the femoral component 30, suchas internal surfaces 15 a-d, may be constructed of solid metallicmaterial, such as titanium as an example, while the remainder of thevoid filling prosthesis 10 may be constructed of porous metallicmaterial.

FIGS. 5 and 6 depict an alternative embodiment wherein the bone voidfiller 10′ does not include selectively removable portions 20 a-d, buthas substantially the same geometries as prosthesis 10. This embodimentmay also be constructed from the same materials as that of prosthesis10, including portions of porous metallic material. Further, thisembodiment may also be constructed from solid metal or high strengthpolymeric material.

FIGS. 7-10 depict the interface between the void filling prosthesis 10,10′ and a femoral component 30. The femoral component 30 may be anyfemoral component 30, for example a femoral component 30 utilized in aposterior stabilized or total stabilized total knee prosthesis, forexample the Scorpio® TS femoral component (Howmedica Osteonics, Mahwah,N.J.).

The void filling prosthesis 10, 10′ may be placed in contact with thefemoral component such that aperture 18 of the central body 11 is placedover a stem portion of the femoral component 30 and the inner surfaces15 a-d are placed in contact with the cam box 33. In one embodiment,bone cement is placed between the inner surfaces 15 a-d and the cam box33 to provide for additional support. Such inner surfaces 15 a-d may beterraced to provide more surface area for bonding to the cement.

In one embodiment, the distal ends of the legs 12, do not contact thebone contacting surface 35 of the femoral component in order to providesome space for bone cement to flow and to provide space so that theoperator can make minor corrections to the rotation of the femoralcomponent 30.

A set of guided instruments may be provided to form the bone void toreceive the void filling prosthesis. Included in this set of instrumentsmay be an IM reamer 40, a boss reamer 50, a reamer guide assembly 60, analignment handle 90, an alignment pin 100, a lobe reamer assembly 110,and a lobe trial 120.

The IM reamer 40, as depicted in FIG. 11, may include a shaft 42 thatincludes a plurality of depth indicators 44 situated along the length ofthe shaft 42 at designated intervals, and a reamer head 43 disposed atone end of the shaft. The other end of the shaft 41 may be configured tointerface with a torque applying device, such as the chuck of a drill.

The boss reamer 50, as depicted in FIG. 12, may include a cannulatedshaft 52 that includes a boss reamer head at one end. The other end 51of the shaft 52 may be configured to interface with a torque applyingdevice, such as the chuck of a drill. The internal diameter of thecannulated shaft 52 is such that the shaft 52 may be slid over the IMreamer shaft, but generally not the IM reamer head, and rotated withrespect to the IM reamer. The boss reamer head may also be cannulated toslide over the IM reamer shaft 42 and may have a cutting diametersubstantially similar to the diameter of the central body 11.

The reamer guide assembly 60, as depicted in FIGS. 13-19, may include atrial stem 70 and a reamer guide 80. The reamer guide generally includesa base 82, a support shaft 81, and a guide block 88. The trial stem 70may be connected to one end of the base 82. In one embodiment, thisconnection may be a threaded connection, ball-detent connection or anyother connection as is known in the art. The other end of the base 82includes an abutment surface 89 and the support shaft 81 extending fromthe base 82 at an outward angle with respect the longitudinal axis ofthe trial stem 70. The support shaft 81 then bends such that theremainder of the support shaft 81 is generally parallel to thelongitudinal axis of the trial stem 70. Integrated into the end of theguide shaft 81 is the guide block 88. The guide block 88 generallyincludes a handle hole 83 extending through the guide block 88 forreceipt of an alignment handle 90 (described below), an alignmentpinhole (not shown) for receipt of an alignment pin 100 (describedbelow), and a first and second lobe reamer guide 84, 85. The first andsecond lobe reamer guides 84, 85 are generally disposed between thehandle hole 83 and alignment pinhole. Both the first and second lobereamer guides 84, 85 include a passageway 86 a, 86 b that issubstantially cylindrical and a side-slot 87 a, 87 b extending throughthe sides of each of the lobe reamer guides 84, 85 into the passageway86 a, 896 b. The longitudinal axes of the passageways 86 a, 86 b extendto a location on the abutment surface 89. Further, these longitudinalaxes may be provided at various angles with respect to the longitudinalaxis of the trial stem 70 in order to ream different bone voiddimensions.

The alignment handle 90, as depicted in FIG. 14-19, is generally anelongate shaft with a flange disposed 91 along its length for abuttingagainst the guide block 88. The alignment pin 100 is preferably a ⅛″diameter pin with a length long enough to extend beyond the epicondyleswhen inserted into the guide block 88. While ⅛″ diameter is preferred soas to not obstruct the epicondyles from the operator's view, anydiameter pin may be used.

The lobe reamer assembly 110, as depicted in FIGS. 15-17 and 19,includes a lobe reamer head 117, a reamer shaft 116, a depth stop collar112, and a bushing 113. The lobe reamer head 117 is disposed at one endof the reamer shaft 116, while the other end 111 of the shaft 116 isconfigured to interface with a torque applying device. The depth stopcollar 112 is fixed to the reamer shaft 116 opposite the end of the lobereamer head 117. The reamer shaft 116 has a diameter small enough to fitthrough the side-slot 87 a, 87 b of the first and second reamer guides84, 85. The bushing 113 is disposed along a portion of the reamer shaft116 between the reamer head 117 and depth stop collar 114 such that thebushing 113 can slide back and forth between the reamer head 117 anddepth stop collar 112. The bushing 113 is generally cylindrical andincludes a first segment 115 and second segment 114 where the secondsegment 114 generally has a larger diameter than the first segment 115.The diameter of the first segment 115 may be dimensioned to slide intoand fit tightly within the passageway 86 a, 86 b of the first and secondlobe reamer guides 84, 85.

The lobe trial 120, as shown in FIGS. 18 and 19, includes a lobe trialhead 125 and a first shaft segment 124 and a second shaft segment 122.The lobe trial head 125 d is disposed at the end of the first shaftsegment 124 and generally has a frustoconical shape with a portionremoved along its length. The lobe trial head 125 is dimensioned tosubstantially match the bone void formed by the reamer head 116 and tosubstantially match at least one leg 12, 13 of the void fillingprosthesis 10. While the lobe trial head 125 is depicted as having thisshape, the lobe trial head 125 may have any shape depending on the shapeof the reamer head 116 and the legs 12, 13 of the void fillingprosthesis 10. The first shaft segment 124 has a diameter less than thatof the second shaft segment 122 and is dimensioned to be capable ofpassing through the side-slot 87 a, 87 b of the first and second lobereamer guides 84, 85. The second shaft segment 122 is dimensioned suchthat it can tightly fit and slide within the passageway 86 a, 86 b ofthe first and second lobe reamer guides 84, 85. An impact surface 121 isformed at the opposite end of the lobe trial 120 as that of the lobereamer head 125. The impact surface 121 is a relatively broad andflattened surface so that the operator can impact the lobe trial 70 inorder to seat the lobe trial head 125 into a bone void.

In one embodiment of the present invention, a method for forming a voidin bone to receive the void filling prosthesis 10, as illustrated byFIGS. 11-19. In this embodiment, the instruments, as described above,are utilized. While FIGS. 11-19 and the following description of themethod are directed toward the preparation of a bone void within afemur, it is to be understood that this is merely an example. Thefollowing method may be utilized to prepare a bone void in any longbone.

Referring to FIG. 11, the IM reamer 40 is depicted as reaming along theIM canal of a femur 200 until the bone 200 is flush with the requisitedepth indicator 44. While it appears from FIG. 11 that the IM reamer 40is passing through a femoral component, the femoral component is merelya depiction of the femur 200. With the IM reamer 40 remaining within theIM canal, the boss reamer 50 is slid over the shaft of the IM reamer, asshown in FIG. 12. The operator reams along the IM reamer shaft 42 untilthe boss reamer head 53 abuts the IM reamer head 40, thereby preventingfurther travel into the femur bone 200. The IM reamer and boss reamer 50are then removed from the IM canal in preparation for further boneforming.

Referring to FIG. 13, the reamer guide assembly 60 is assembled. In suchassembly, the operator may select a trial stem 70 to match the IM reamerhead diameter, and then attach the trial stem 70 to the reamer guide 80.In another embodiment, the IM reamer 40 may be attached to the reamerguide 80, thus taking the place of the trial stem 70. Attachment may beby a threaded engagement, with a ball detent, or any other engagementknown in the art. Once the reamer guide assembly 60 is assembled, thetrial stem 70 is inserted into the portion of the IM canal that wasreamed by the IM reamer 40, and the base of the reamer guide 82 isinserted into the portion of bone reamed by the boss reamer 50. Theoperator may further seat the reamer guide assembly 60 to the properdepth by impacting the end of the guide block 88. The proper depth maybe indicated when the reamer guide assembly 110 no longer moves whenimpacted and generally where the bone is flush with the bend in thesupport shaft 81.

Referring to FIG. 14, with the reamer guide assembly 60 firmly seatedwithin the IM canal, the alignment handle 90 is placed in the handlehole 83 until the flange 91 abuts the guide block 88, and the alignmentpin 100 is placed in the alignment pinhole such that the alignment pin100 extends from both sides of the guide block 88 beyond the peripheryof the femur. The operator will then grip the alignment handle 90 androtate the reamer guide assembly 60 within the IM canal until thealignment pin 100 is aligned with the transepicondylar axis or any axisof the operator's preference.

Referring to FIG. 15, once alignment is achieved the lobe reamerassembly 110 is loaded into the first lobe reamer guide 84. This isachieved by moving the bushing 113 so that it abuts the depth stopcollar 112, thereby exposing the reamer shaft 116 proximate to thereamer head 117. The reamer shaft 116 is then side-loaded through theside-slot 87 a and into the passageway 86 a. The resulting configurationshould be such that the reamer head 116 is located on one side of thefirst lobe reamer guide 84 and the bushing 113 located on the otherside, as shown in FIG. 15. The first segment 115 of the bushing 113 isthen slid into the passageway 86 a until the second segment 113 abutsthe first lobe reamer guide 84, as shown in FIG. 16. The reamer head 116is then advanced into the distal femur by applying a torque to thereamer shaft 115 until the depth stop collar 112 abuts the bushing 113and the reamer head 116 abuts the abutment surface 82, as shown in FIG.17. The reamer head 116 is then retracted from the femur and the reamerassembly 110 removed from the first lobe reamer guide 84 through theside-slot 87 a.

Referring to FIG. 18, the lobe trial 120 is then loaded into thepassageway 86 a of the first lobe reamer guide 84 in a similar fashionas the lobe reamer assembly 110. The first shaft segment 124 of the lobetrial 120 is passed through the side-slot 87 a and into the passageway86 a. The lobe trial head 125 is then advanced into the first bone void.As the lobe trial head 125 is advanced, the second shaft segment 123 isadvanced into the passageway 86 a and the lateral protrusion 123 isadvanced into the side-slot 87 a. The lateral protrusion 123 ensuresthat the lobe trial 120 has the proper rotational alignment and alsoacts as a stop to prohibit rotation. In one embodiment of the lobe trial120, the lateral protrusion 123 may be a pin that extends through thesecond shaft segment 122 and into a hole located in the first lobereamer guide 84 to prevent both rotational and translational movement.The operator may then impact the impact surface 121 to fully seat thelobe trial 120. The lobe trial 120 may remain in place while a secondbone void is formed in order to provide additional stability duringreaming, as seen in FIG. 19.

Referring to FIG. 19, the lobe reamer assembly 110 is side-loaded intothe second lobe reamer guide 85 as previously described. The reamer head117 is then advanced into the distal femur by applying a torque to thereamer shaft 116 until the depth stop collar 112 abuts the bushing 113and the reamer head 117 abuts the abutment surface 89, thereby forming asecond bone void for receipt of the void filling prosthesis 10.

While this method has generally been described herein as utilizing onelobe reamer assembly 120 to form both bone voids, more than one lobereamer assembly 110 having different geometries may be used depending onthe geometry of the void filling prosthesis 10.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A method of forming a bone void for receipt of a prosthesis,comprising the steps of: inserting a stem of a reaming guide assemblyinto an intramedullary canal of a bone, the reaming guide assemblyhaving first and second reamer guides disposed adjacent to each other,the first and second reamer guides being connected to an end of thestem; reaming the bone through the aperture of the first reamer guide toform a first bone void; inserting the lobe trial into the first bonevoid; and reaming the bone through the aperture of the second reamerguide to form a second bone void.
 2. A system for reaming bone,comprising: an intramedullary member having first and second ends and alongitudinal axis extending in a first direction between the first andsecond ends; and a guide member coupled to the first end of theintramedullary member and having a body, the body having first andsecond apertures each extending entirely through at least a portion ofthe body, the first aperture having a first length defining a firstaxis, the second aperture having a second length defining a second axis,the first and second apertures being oriented with respect to theintramedullary member such that the first and second axes each extend inthe first direction and are offset from the longitudinal axis of theintramedullary member.